In the food industry, encapsulation may be used to stabilize the core material, and to control the timing and rate of the release of the core material. Thus, encapsulation makes it possible to protect sensitive food components, to ensure against nutritional loss and to mask or preserve flavors and aromas. Encapsulation also increases the stability of vitamin or mineral supplements, for example, which are normally sensitive to UV radiation, light, oxygen, metals, humidity and temperature. Moreover, encapsulation is also utilized in the pharmaceutical industry to protect the lining of the mouth and oesophagus from harsh orally administered drugs which are released in the stomach by the action of stomach acids and enzymes on the capsule coating, or for controlled release of drugs delivered through intramuscular, subcutaneous or intravenous routes.
Proteins (whey, soy, gelatin, egg albumin, casein, human serum albumin etc.) and polysaccharides (starch, carboxymethyl cellulose etc.) have been used as wall materials for the encapsulation of various ingredients. A review of the techniques used is given by Gupta, P. K. and Hung, C. T., "Albumin Microspheres: applications in drug delivery," J.Microencapsulation, (1989), 6, 464-472 and R.Arschady, "Albumin Microspheres and Microcapsules: Methodology of manufacturing techniques," Journal of Controlled Release, 14 (1990) 111-131. Typically, the active ingredient is dissolved, emulsified or dispersed in a solution of protein in water and then the protein is denatured and becomes water insoluble, thus entrapping the active ingredient. Depending on the desired capsule shape and size, various techniques are also described in the literature ranging from simple grinding to forming double emulsions in oil media prior to denaturation. However, it is common in all techniques that the denaturation process is performed either by heat (100-180.degree. C.) or by chemical crosslinking with suitable crosslinking agents such as glutaraldehyde. It is clear that heat denaturation is not suitable in the case of heat sensitive active ingredients such as some vitamins, aromas, flavors or drugs such as methotrexate, epinephrine, salbumatol is discussed by Gupta and Hung "Albumin Microspheres: Physico-chemical characteristics," J.Microencapsulation, (1989), 6 427-461. Chemical crosslinking is also not suitable when the use of chemicals is not approved by food or drug regulations.